Wireless network, including wireless metropolitan area networks (WMAN) such as those compliant with the IEEE standard 802.16.x (WiMAX), may use multiple antennas on the transmitters and receivers, referred to as Multiple-Input Multiple-Output (MIMO), to communicate in order cancel interference from adjacent cells. Wireless networks may communicate using Orthogonal Frequency Division Multiplexing (OFDM) signaling. An OFDM signal is comprised of multiple sub-carriers each modulated at a symbol rate equal to the reciprocal of the frequency separation. MIMO schemes are often implemented with OFDM signaling as OFDM provides for easy characterizing of channel frequency response.
For wireless transmissions where high data rates and high signal to interference and noise ratio (SINR) are desired, a wireless MIMO receiver may operate in a spatial (de)multiplexing (SM) mode to estimate the transmitted signal. For wireless transmissions where increased coverage at low SINR is desired, the wireless MIMO receiver may operate in a space-time block (de)coding (STBC) mode. In order to match the transmission to the channel conditions, the MIMO receiver scheme may switch between SM and STBC modes (detection modes) and/or may adapt the number of received sub-streams (RF chains) depending on the operating power mode and channel conditions. The MIMO receiver may need to switch between the detection modes with minimum latency.
The MIMO receivers may include a plurality of different detectors (e.g., maximum ratio combining (MRC), minimum mean squared error (MMSE), maximum likelihood (ML)) to account for the different MIMO modes. The appropriate detector may be enabled based on the spatial operational MIMO mode. Having multiple MIMO detectors requires silicon area for each detector and may require complicated data interfaces.